Katy was pictured in some of Alba and Hudson's snapchat photos, but beau Orlando kept a low profile.

"They were arm in arm and looking very in love...They looked like regular tourists, just strolling and enjoying themselves," an eyewitness told E! News.

Orlando also reportedly took to the slopes for a few hours of snowboarding while the couple were ensconced in Aspen. .

Although neither celebrity have confirmed their romance, they have enjoyed a series of trips together.

In February they vacationed in Hawaii and in March they travelled to England where Katy met his mother and sister. They then visited Katy's hometown of Santa Barbara, and have also been to Disneyland together.

"Katy and Orlando enjoy travelling together, so whenever they have an opportunity they try to make it work," the source added. "All of Katy's friends and family like Orlando, so bringing him away with her is always a great time."